A campus trespassing call in Ontario turned into an explosives investigation. Here's what to know

For nearly two weeks, a beige home on the corner of a snowy street in London, Ont.'s quiet Medway neighbourhood has been the epicentre of a bizarre police investigation that has spread from the local university campus to Ottawa, Quebec and the RCMP's national security unit.

The investigation began with a late-night trespassing accusation from Western University grounds and led to police discovering what they described as hazardous chemicals that could be made into explosives. A slew of charges against four people ensued.

Here's more of what to know about the case.

Officers with the London Police Service (LPS) said they were called to Western's campus around 1:40 a.m. ET on Jan. 24 to assist campus police with a trespasser who was taken into custody. Officers arrested a man who tried to run away and seized a loaded handgun, according to the service.

Police later learned a second man had been involved. A statement said a further investigation led officers to 212 Chesham Place, where police took two more people into custody after finding the chemicals.

Previously, Sean Travis, the LPS's acting detective superintendent, told reporters at the scene that observations made in the home caused "concern about chemicals that could be used to create explosive devices, not that devices were located."

Last week, the LPS announced a total of over two dozen charges against:

They are all current or former students at Western University. The three men have various engineering degrees; Ji, the only woman charged, was set to graduate next year.

Wang, Han and Ji all live at the Chesham Place address, according to court records. On Friday, a news briefing led by London police Deputy Chief Paul Bastien was told Tong is "heavily associated to the Chesham Place address," but no other information was provided.

You can read more about the four accused here.

The three men were developing an anti-drone weapon system they hoped to pitch to investors, CBC News learned this week.

In a video posted to YouTube three months ago, Tong, Wang and Han explained they were in the process of designing a military system meant to prevent drone attacks and looking for funding.

“We’re taking on the challenge of stopping weaponized drones,” said Tong in the video titled MORSLAB Pitch Presentation. “MORSLAB is in the right place at the right time, and we hope you can join us.”

Tong goes on to say that the team runs a garage CNC mill and has its own “chemical lab on site.” The video also includes clips of Wang working on the system in the bed of a pickup truck that CBC News has verified was parked at 212 Chesham Place.